Prior art power supply arrangements comprising a plurality of switching mode power supply units connected in parallel to one or several loads by means of shielded conductors generate high electromagnetic interference (EMI). Said EMI can degrade the performance of adjacent electrical or electronic equipment. The terms noise and radio-frequency interference (RFI) are sometimes used in the same context. The EMI generated by the power supply system can be propagated either by conduction via the input and output conductors, by the ground points, or by radiation from the casings and/or conductors.
The known solution to this problem is to apply filters to the output terminals of each power supply unit and/or input terminals of the at least one load. These filters however bring about several problems: They are bulky and have relatively high weight. This problem also increases with the amount of power supplied by the power supply unit, mainly because of the magnetic filter components. This is particularly disadvantageous in airborne, space and other applications where weight and size are important factors. Another problem is that extensive testing of filter component combinations is necessary to accomplish adequate power supply noise reduction, because filter components are not ideal. It is also necessary to perform measurements on the individual power supply units connected in parallel to at least one load to determine if the power supply units comply with EMI regulations. This implies that for testing purposes, you need one filter prototype for each power supply unit in your power supply system. Testing and verification is thus costly and labour intensive.
There is consequently a need for a method for reducing electromagnetic interference radiated from a power supply arrangement, as well as for an improved power supply arrangement, which overcomes the above mentioned problems.